No Opacity mask when rendering 3d imposter sprites (Render To Texture BP)

Hi everyone. When I try to render imposter for my tree model using RenderToTexture_LevelBP there isn’t opacity mask in the output. I selected Decal Mask in capture settings, but it doesn’t work, opacity mask image don’t appear in the file browser. Thanks.
P.S. sorry for my bad English

render preview problem in 4.24 any idea we check 4.24 and 4.25 but both same problem movie render preview not show video but output video is fine any idea preview window size change???